Windows 2003 DCPROMO Fails: “Version of the active directory schema of the source forest is not compatible”
This issue may occur when Active Directory has not been updated with the Windows Server 2003 R2 schema extensions.
To resolve this issue, run the adprep.exe /forestprep command from the Windows Server 2003 R2 installation disk 2 on the schema master. To do this, insert the Windows Server 2003 R2 installation disk 2, and then type the following command:
Once, complete, rerun your DCPROMO and the issue should be resolved.